MAbs are typically prepared by in vivo cultivation of hybridomas in the peritoneal cavity of mice as ascitic rumours (Goding, 1980), which produces antibody concentrations of the order of 20 mg/ml. The simplicity, efficiency, and high concentration of the final product make ascitic fluid the preferred choice for laboratories requiring relatively small amounts of a large number of MAbs. There are ethical reasons to look for alternatives, but it would in any case be attractive to develop a simpler, and possibly cheaper, alternative tissue culture method capable of substituting ascitic fluid.
One known tissue culture method for MAb production involves growing hybridoma cultures to large volumes in roller bottles, and then concentrating the antibodies produced by use of ammonium sulphate precipitation. With this method, the cells can only be maintained healthily below 10.sup.6 /ml. Another method involves concentrating the cells to 2.times.10.sup.6 cells/ml or more in serumless medium for 3-4 days (Galfre and Milstein, 1981). This can improve the yield, and has added advantages in that the volume of the product is lower, and there are no foreign proteins present (eg. Foetal bovine proteins) to complicate purification. Moreover, these methods are cumbersome, take up valuable space in the incubator, and necessitate the use of large quantities of media, foetal calf serum (FCS), and ammonium sulphate.
Hollow fibre systems allow cells to be grown between narrow diameter hollow fibres, within a cartridge into which fresh medium is continuously pumped. Hybridomas can reach high densities, and production of MAbs is efficient (Schonherr and Gelder, 1988) However, the cost of such systems with associated software is high, and only justified when relatively large amounts of individual MAbs are required. This is also the case with fermenters and bioreactors. Growth of cells in dialysis bags within small culture bottles (Sjorgren-Jansson and Jeanson, 1990), although appropriate for laboratory use, is restricted to 25 ml per bottle.